We made our first hardware by hand, i believe we did 15 units. I remember my cofounder broke down because he couldn’t take the pressure of receiving fifteen orders and now we had to make FIFTEEN by hand, lol. But we were able to figure out SO MANY issues before mass production. And of course even then many slipped through
https://jlcpcb.com/3d-printing/?gad=1
But if you must:
Metal printing has been available for awhile. =3